As a cooling device for an internal combustion engine, there is a cooling device including an external passage (i.e., bypass passage) that circulates the cooling water for the internal combustion engine without passing the cooling water through a radiator, to accelerate warming of the internal combustion engine. There is another cooling device which accelerates warming of an internal combustion engine by stopping a circulation of the cooling water during a warming of the internal combustion engine.
However, according to investigations, the inventors of the application found that there is a possibility that the temperature, which previously increased before starting the circulation of the cooling water, of the internal combustion engine is temporarily decreased because low-temperature cooling water flows into the internal combustion engine when the circulation of the cooling water is started from a stopped state of the circulation of the cooling water during a warming of an internal combustion engine.
A countermeasure against the temporary temperature decrease of the internal combustion engine is described in Patent Literature 1 (JP 2011-214566 A), for example. According to Patent Literature 1, when the circulation of the cooling water is started, the opening degree of a flow adjustment valve is controlled such that the lower the temperature of the cooling water flowing into an internal combustion engine (i.e., inflow temperature), the lower the flow rate of the cooling water, and the higher the temperature of the cooling water flowing out of the internal combustion engine (i.e., outflow temperature), the higher the flow rate of the cooling water.